The present disclosure relates to a valve unit for a coating installation, e.g. an integrated colour changer or two-component mixer in a rotary atomizer.
A rotary atomizer with an Integrated Colour Changer (ICC) is known from WO 2007/131636 A1 and corresponding U.S. Pat. Pub. No. 2009/0158998A1, wherein the colour changer is structurally integrated into the housing of the rotary atom-izer. Furthermore, an annular design for a colour changer of this type is known from WO 2008/071273 A2 and corresponding U.S. Pat. Pub. No. 2010/0012025A1, wherein the colour changer is formed by a valve unit which is accommodated in a housing. The known valve unit here essentially consists of a central coating agent channel, into which a plurality of coating agent supply lines open, wherein the feed from the individual coating agent supply lines into the central coating agent channel is controlled by radially running needle valves. The housing of the valve unit usually consists of plastic (e.g. POM: polyoxymethylene), wherein the valve receptacles, the valve seats, the central coating agent channel and the coating agent supply lines are constructed in the housing of the valve unit, which consists of plastic. The conventional design of the valve unit with a housing consisting completely of plastic has various disadvantages however, which are briefly explained in the following.
One disadvantage of this conventional design consists in the plastic of the housing only having an unsatisfactory material resistance with respect to the paints and rinsing agents used, as the paints or rinsing agents can attack the plastic and degrade the material over time.
A further disadvantage of the previously described conventional design of a valve unit consists in a material thickness of the housing of a spacing, in one case at least 2 millimeters (mm), having to be maintained between the adjacent valve receptacles in the housing of the valve unit, in order to ensure a satisfactory stability. This has the disadvantage, however, that the packing density of the valves in the housing is limited, which is disadvantageous in particular in the case of a structural integration of the valve unit into a rotary atomizer, as the available installation space is limited there.
A further disadvantage of the previously described conventional design of a valve unit is of significance in particular if the valve unit is not used as a colour changer, but rather as a two-component mixer, in order to mix a base paint with a hardener. Here, the valve unit must namely be cleaned regularly in order to prevent the base paint from hardening within the valve unit, which would lead to a total loss of the valve unit. This cleaning of the valve unit, however, holds the danger that the valve seat is damaged or even destroyed by means of the cleaning process.
A valve unit with two housing parts, which both consist of plastic however, is known from U.S. Pat. No. 3,870,233.
Further, painting installation components are known from DD 276 038 A5 (and corresponding U.S. Pat. Nos. 4,955,960 and 5,085,373), DE 698 27 611 T2 (and corresponding U.S. Pat. No. 6,284,047 B1), DE 10 2005 033 191 A1 (and corresponding U.S. Pat. No. 7,712,484 B2), and EP 2 110 177 B1 (and corresponding U.S. Pat. Pub. Nos. 2008/0121740A1, 2009/0026293A1, 2009/0032625A1, and 2010/0193613A1), which to some extent consist of different materials. However, these references are not concerned with valve units such as those described herein according to the exemplary illustrations.
Accordingly, there is a need for a correspondingly improved valve unit.